Compact rotary seal

ABSTRACT

This invention relates to simple, compact rotary seals that contract to maintain a seal as the sealing elements may wear over time. Embodiments of this invention allow simple elastic rings, such as an O-ring, to be used as the sealing element.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. Ser. No. 15/610,775 filed Jun.1, 2017 based upon and claiming priority to U.S. Provisional ApplicationSer. No. 62/344,355 filed Jun. 1, 2016, the disclosures of which arehereby incorporated in their entirety by reference herein.

BACKGROUND OF THE INVENTION

The invention addresses cutting tools used to remove material such asfrom a workpiece or bulk feedstock. More specifically, it addresses suchtools that employ a round cutting insert that rotates under the force ofthe material removal process as a result of the cutting insert beingaffixed to a support device that permits rotation about the axis of thecutting insert. The most basic representation of a round cutting insert1 is depicted in FIG. 1a ; it is fundamentally a disk having anaxisymmetric peripheral surface 2, two axisymmetric end surfaces 3, andinsert axis 4 about which said surfaces are axisymmetric. One or boththe end surfaces 3 can be partially or entirely non-planar and theperipheral surface 2 may also be non-cylindrical, one example of whichis shown in FIG. 1b . There are two basic configurations for machiningwith a round cutting insert. A conventional radial mount is shown inFIG. 2 (a face milling tool as an example) where flank surface 5 is theperipheral surface 2 and rake surface 6, the surface on which the chipof removed material is formed, is one of the end surfaces 3. This typeof configuration is the subject of numerous patents, such as U.S. Pat.No. 2,885,766A, 3,329,065, 4,477,211, 5,478,175. The other configurationis a tangential mount as shown in FIG. 3 (a face milling tool as anexample) where rake surface 6 is the peripheral surface 2 and flanksurface 5 is one of the end surfaces 3. This type of configuration isthe subject of numerous patents, such as U.S. Pat. Nos. 2,217,523,2,233,724, 2,551,167 and 4,223,580 for single-point lathe processes usedto create surfaces of revolution and more recently U.S. application Ser.No. 14/502,035 for a variety of multi-tooth processes where compactnessof the rotary support device upon which the round cutting insert isaffixed is important, as compared to many lathe applications. In allcases, the circular intersection of flank surface 5 and rake surface 6defines a round cutting edge 7. Generally, for a rotating round cuttinginsert, there must be a central hole 8 to facilitate mounting cuttinginsert 1 to rotary support device 21.

When machining, heat energy is generated by friction and deformation ofthe workpiece material (i.e., the cutting process) that is then impartedfrom the cutting process into the cutting insert. As the rate of heatgeneration in the process increases, such as by running the cutting toolat a higher cutting speed, the temperature of the tool (i.e., thecutting insert) increases. Increased temperature is a primary cause ofincreased tool wear rate. Allowing the cutting insert to rotate helps tomoderate the effect of heat energy generated by the cutting process,extending tool life and/or allowing the cutting tool to operate athigher speed without excessively compromising tool life. Rotation of thecutting insert without human intervention also allows the entirecircumference of the round cutting insert, the round cutting edge, to befully consumed with no need for human intervention to rotate to freshregions of the circumference (referred to as indexing), which isrequired for non-rotating cutting inserts.

The need for a rotary support device that constrains five degrees offreedom while allowing one degree of freedom to be free, that is, thenoted rotation about the axis of the round cutting insert, addsmanufacturing cost to the cutting tool. Keeping manufactured cost lowenough so that the increased performance of a rotating-insert cuttingtool is sufficient to justify its added purchasing expense has been aconsistent challenge in previous attempts at commercializing suchcutting tools. A main driver of this challenge is the extremeoperational demands on the rotary support device, the cutting insert,and the cutting insert's connection to and interface with the rotarysupport device. The present invention addresses the numerous pastshortcomings in meeting the operational demands in a manner that isgeometrically compact and cost effective.

One of the main challenges is that the rotary support device, and thecutting insert itself, must mechanically support the high cuttingprocess forces. For the cutting insert, ample cross-section is requiredso that it does not crack, and a larger cross-section consumes more ofthe limited space available. For the rotary support device, thechallenge lies in transmitting/supporting the noted forces across itsinternal surfaces that allow relative rotary motion to occur whileconstraining all other motions, and at the same time maintainingsufficient cross-sections to avoid cracking or other deformationfailure, again, all this being achieved in the limited space available.

Relative rotary motion is provided by “bearings”. In plain bearingsstatic friction between two mating bearing surfaces is overcome to allowrelative motion due to sliding. In rolling-element bearings relativemotion occurs due to rolling of round elements (e.g., balls/spheres,cylinders, or frusto-conical (tapered) solids/rollers) between the twobearing surfaces. Commercial-off-the-shelf rolling-element bearingsincorporate the bearing surfaces into components referred to as“raceways” or races, for short. For rolling-element bearings there isminimal (in some cases theoretically zero) sliding friction. Therotating-insert cutting tool application requires extremely compactpackaging of the bearings relative to commercial standard bearings thatwould be specified to support forces of the magnitude seen from thecutting process. Thus, to summarize, one of the longstanding challengesthat have inhibited the widespread practical commercial adoption ofrotating-insert cutting tools is the need to arrange and package thebearings very compactly while being able to support the high forceswithout catastrophic failure or a limited fatigue life.Commercial-off-the-shelf rolling-element bearings generally do not existto such optimal levels of load bearing capacity, in the needed degreesof freedom, relative to the size of the bearing; that is, there is notsufficient market to motivate bearing companies to design and producesuch size-optimized bearings, at least not for most metal-cuttingapplications where it is preferred or required that the cutting insertbe small (for example and without limitation, less than 25-30 mm indiameter). For example, in U.S. Pat. No. 4,477,211 for a “rotary toolcutting cartridge”, the rotary support device (the rotary tool cuttingcartridge) employs lower and upper rolling-element thrust bearings andradial needle-roller bearings that make use of a specially designedhousing as the bearing raceways and in such a way as to maximize thenumber of rolling elements. Still, while space is saved by not using apre-packaged off-the-shelf bearing and rather using a special-purposehousing, that housing exhibits significant bulk in its cross-section.

Another significant shortcoming in past attempts at commercialapplication of rotating-insert cutting tools is contamination of thebearing surfaces noted above. Particles of removed material, dust, andeven metal working fluid, that infiltrate from the working environmentinto the bearings can have a deleterious or even catastrophic (seizingthe relative motion) effect. In general applications where relativerotary motion occurs between plain and/or rolling-element bearings, thebearing surfaces are packaged in such a way as to seal out externalcontamination. Rotary seals that are very compact are difficult to findwith the exception of those that are built into standard bearings that,as noted, generally do not meet the size/packaging needs of thisapplication. Thus, a specially designed rotary support device requiresthe use of either standard seals or specially designed seals. The formerare available, like bearings, in general purpose designs that are not ascompact as desired, and the latter are either very expensive or, in atleast some known examples, result in excessive friction, wear andreduction in sealing performance over time. For example, U.S. Pat. No.4,477,211 employs an O-ring to seal the lower end of the rotary supportdevice (referred to as a “cartridge” in the reference) or, as analternative, a C-ring. The product based on this patent and sold byRotary Technologies Corp. ultimately employed a C-ring seal thatconsumes 1.4 mm radially and 2.5 mm axially. A second-generation productoffered by Rotary Technologies Corp., based on U.S. application Ser. No.12/350,181, actually does use an O-ring, as called out in thatapplication. While it seals well, and is more compact (0.9 mm radiallyand 1.0 mm axially), it is extremely tight causing significant friction.In fact, the O-ring approach to a rotary seal, while elegant and simple,is not a usual use of an O-ring, and is not well suited due to thetypical tolerances on the cross-sectional size of the O-ring section. Asa result, accommodating the noted tolerance requires the seal to beexcessively tight/compressed at one end of the tolerance band. It thenwears significantly and eventually may lose its sealing ability due towear.

Along with the challenge noted to support the cutting process forces bythe rotary support device is the consideration of what it means to“support” the forces. Metal-cutting (and when cutting materials otherthan metal in order to produce a new surface intended ultimately forsome function) requires the support of those forces to be stiff enoughthat the deflection of the cutting insert relative to the workpiece(tool-work deflection) is small enough to provide acceptable results.First, the rigidity must be sufficient to avoid unstable vibrations inthe noted tool-work deflection, referred to as chatter. Second, therigidity must be sufficient to avoid tool-work deflection large enoughthat the dimension and/or surface finish of the machined surface featuredo not meet the specified tolerances, which in many cases are fairlytight. For past implementations of rotating-insert cutting tools,maintaining precision of the produced surface has been a challenge dueto the need to maintain a relatively rigid support of the cutting insertin five degrees of freedom (three translational, two rotational) whileallowing it to also freely move in the sixth degree of freedom (rotationabout the axis of the round cutting insert). The bearing arrangementnoted in U.S. Pat. No. 4,477,211, where radial bearings are used alongwith axial thrust bearings, is common across known attempts at applyingrotating-insert cutting tools. While it is routinely possible to applyan axial preload to eliminate axial clearance/slop in the rotary supportdevice, that is not possible in the radial direction when using a radialbearing. This is critical in that the cutting insert is then notcompletely constrained in all the degrees of freedom other than that ofthe cutting insert axis of rotation. The result is a compromisedfinish/roughness on the surface produced; often there are smallserrations or waves that fully (six-degree-of-freedom) constrainedcutting inserts do not produce. No realistic tolerance on the diametricsurfaces between which radial rolling elements are located can eliminatethe noted radial clearance/slop.

Also posing a challenge in regard to precision in the machined surfaceis how well the round cutting insert is centered/concentric about therotary axis of the rotary support device. This is largely influenced bythe means of how the cutting insert is located on the rotating portionof the rotary support device (in the configurations considered here,that is referred to as the “rotor” as it rotates relative to the fixed“stator”, and the cutting insert is affixed to and located by therotor). Many past attempts at commercial rotating-insert cutting toolsrequire an inner diameter of the cutting insert to match the outerdiameter of a mating element, such as the rotor, in close slip-fittolerance while that inner diameter of the cutting insert must alsoexhibit a close/tight concentricity tolerance relative to the roundcutting edge. Of course, this all also presupposes that the innerbearing surface of the rotor is closely concentric to its outerdiametric surface to which the insert is located by its inner diametricsurface, and that there is minimal radial clearance/gapping between theneedle rollers and the rotor inner diametric surface and the supportingdiametric surface of the stator. All these noted requirements for closetolerances and concentricities add cost to the rotary support deviceitself and the cutting insert, and for the usual radial bearing nopractical tolerance can eliminate the radial bearingclearance/gapping/slop noted above. As noted, one of the main commercialchallenges in rotating-insert cutting tools is their high cost, both inthe cutting tool (rotary support device) itself and in thedisposable/perishable cutting inserts.

Another less quantifiable challenge to successfully meeting the needs ofa commercial market with rotating-insert cutting tools is their ease ofuse. Compared to traditional fixed (i.e., non-rotating/nonmoving)cutting inserts (relative to the cutting tool body to which they areattached) rotating-insert cutting tools have inherent complexity.Furthermore, due to the inherent potential for rotation of the cuttinginsert relative to the rotor, provisions must exist that eliminate thepotential for the cutting insert to become loose or disconnected fromthe rotor, such as by loosening of a threaded fastener due to inducedrotation of the cutting insert relative to the rotor that, throughfriction between the cutting insert and a mating threaded fastener thatis threaded onto/into the rotor, causes the threaded fastener to loosenrelative to the rotor. One solution is to use a left-handed fastener toaffix a rotating insert that rotates in a left-handed fashion (andright-handed, vice versa) so the potential insert-rotor relativerotation would serve to tighten the fastener. This requires that aleft-hand version and a right-hand version of the rotary support devicebe made available to customers to serve all types of cutting tool needs.This is the approach taken in the products of Rotary Technologies Corp.based on U.S. Pat. No. 4,477,211.

Another approach is to have one or more threaded fasteners that hold thecutting insert to the rotor in ways that avoid the axis of the threadedfasteners being coaxial with the rotor-insert axis. One manner of takingthis approach was indicated in U.S. patent application Ser. No.12/350,181. In most cases due to size/compactness limitations, thisinvolves small screws and small tools. In the product line that resultedfrom that patent application, to avoid the small screws and tools, acutting insert retention device was devised (not in application Ser. No.12/350,181) that tightens to itself and, in so doing, cinches ontomating geometry on the rotor to clamp the cutting insert against theopposing axially planar mounting surface. As such, any relative rotationbetween the cutting insert and rotor cannot loosen the insert retentiondevice since its threaded tightening happens between two componentswithin the retention device. In the example noted, the insert retentiondevice may work quite well, but it is not familiar to most users,requires special tools, and is of high cost and complexity.

Finally, coming back to cost as an ultimate practical commercial hurdle,a general challenge to any design of such a system is the recognitionthat all the noted challenges must be overcome with special designs thatare economically produced/manufactured at the production volumes thatare generally low relative to commercial, general-purpose bearings andseals, for instance. The present invention takes into considerationthese production volume cost drivers as well.

The domain of application includes various types of cutting tools usedto produce various types of surfaces in various types of work materials.A round cutting insert mounted to a rotary support device may beattached to a cutter body that is rotated at high speed on a machinespindle to perform operations such as, but without limitation, facemilling, end milling, drilling, or cylinder boring. The round cuttinginsert mounted to a rotary support device may also be attached to ashank that is affixed to a lathe to perform OD turning, IDturning/boring or facing. The cutting insert may be oriented relative tothe cutting motion in either a conventional radial mounting or atangential mounting, as noted earlier. In many cases, the “rotarysupport device” may be termed a rotary “cartridge” or “cassette”; it isaffixed to the cutter body, upon which is affixed a cutting insert, tocomprise the cutting tool. For cutting tools like face mills andcylinder boring tools that employ more than one cutting insert, it isoften important that at least one cutting insert be precisely positionedin the depth-of cut direction relative to other cutting inserts. Forthis reason, this invention provides an embodiment that incorporatesadjustability to the rotary support device, which from this pointforward may be abbreviated RSD.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to machining processes used to createchips of material and new surfaces on a workpiece, in particular throughthe use of a cutting tool that employs one or more rotating cuttinginserts. The present invention includes a rotary support device (RSD)with either one or two tapered bearings for fully supporting the radialload and the axial load, in both directions, with bi-directional (axialand radial) preloading to eliminate radial bearingclearance/gapping/slop, and including the option of adjustability toachieve precise positioning in the depth-of-cut direction, in particularfor tangential mount configurations. The present invention also includesa cutting insert with provisions for attaching to a rotor with athreaded fastener by way of an anti-rotation interface that locates thecutting insert on and relative to the rotor using a single-surfaceinterface, unlike prior art where two surfaces (one radial and oneaxial) are used to locate the cutting insert relative to the rotor. Thefinal element of the present invention is a self-tightening,anti-incursion, compact rotary seal that uses a standard/general-purposeelastic ring.

The present invention provides critical new characteristics that addressthe shortcomings that have severely limited the viability of previousattempts at commercializing rotating-insert cutting tools. Specifically,the present invention provides (1) precision load-bearing capacity withhigh manufacturability at low-to-medium production volumes in both theRSD and cutting insert, (2) an anti-loosening insert mounting that issimple and low-cost with the familiar look, feel and function of athreaded fastener (basic screw or nut), and (3) economical low-frictionrotary sealing in the compact space available.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a basic round cutting insert in its most fundamental form.

FIG. 1b is a round cutting insert showing a non-cylindrical peripheralsurface and non-planar end surfaces.

FIG. 2 is a face mill as an example illustration, with the flank surfaceand rake surface called out, in a conventional radial mounting of around cutting insert.

FIG. 3 is a face mill as an example illustration, with the flank surfaceand rake surface called out, in a tangential mounting of a round cuttinginsert.

FIG. 4a is a section view of a rotary support device architecture wheretwo stand-alone tapered roller bearings are held in a housing formingthe stator to radially and axially support and preload the rotor, uponwhich a cutting insert is mounted and supported by two interfaces—onecylindrical and one axially planar—between the cutting insert and rotorupper end and attached with multiple insert fasteners.

FIG. 4b is a section view of a rotary support device architecture wherethe outer raceways (cups) of two tapered roller bearings are integratedwith one another, also serving as the housing (stator), showing also theuse of preload faster(s) that are non-concentric with the rotor axis asa means of avoiding inadvertent loosening of the preload fastener(s),and a cutting insert being mounted to and supported by one convexinterface on the rotor upper end and attached with a single coaxialinsert fastener where the insert receives a protrusion on the rotor thatprohibits gross rotation of the insert relative to the rotor about therotor axis which could otherwise cause the single coaxial insertfastener to loosen.

FIG. 5a is a section view of a rotary support device architecture wherethe rotor is supported axially at its lower end by an axial thrustroller bearing and supported radially and supported and preloadedaxially (and thus radially) at its upper end by one stand-alone taperedroller bearing, where a cutting insert is mounted to and supported byone convex interface on the rotor upper end and attached with a singlecoaxial insert fastener where the insert receives a protrusion on therotor that prohibits gross rotation of the insert relative to the rotorabout the rotor axis which could otherwise cause the single coaxialinsert fastener to loosen.

FIG. 5b is a section view of a rotary support device architecture wherethe rotor is supported axially at its lower end by an axial thrustroller bearing and supported radially and supported and preloadedaxially (and thus radially) at its upper end by one tapered rollerbearing having its outer raceway (cup) integrated with the rotor, wherea cutting insert is mounted to and supported by one convex interface onthe rotor upper end and attached with a single coaxial insert fastenerwhere the insert receives a protrusion on the rotor that prohibits grossrotation of the insert relative to the rotor about rotor axis whichcould otherwise cause the single coaxial insert fastener to loosen.

FIG. 6a is a self-tightening, compact rotary seal.

FIG. 6b is a self-tightening, compact rotary seal.

FIG. 6c is a self-tightening, compact rotary seal.

FIG. 7a is a rotary support device and cutting insert where the outerraceways (cups) of two tapered roller bearings are integrated with oneanother, also serving as the housing (stator), and the tapered rollerbearings employ cylindrical rollers rather than frusto-conical (tapered)rollers.

FIG. 7b is a top view of the rotary support device and cutting insert inFIG. 7a with the fastener spacer and threaded insert fastener removed toreveal another approach to incorporating anti-rotation receivers on thecutting insert and protrusions on the rotor upper end.

FIG. 8 is a field-adjustable rotary support device allowing the cuttinginsert to be adjusted to the desired position along the adjustment-axisdirection.

FIG. 9 is a cutting insert and rotor upper end where the cutting inserthas a convex surface to mate with a concave surface on rotor upper end.

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention that may be embodied in variousand alternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a rotary cutting insert and support device thatcomprise a round cutting insert 1 and a rotary support device (RSD) 21as shown in FIG. 4a . Cutting insert 1 may be of radial mount type whereflank surface 5 (as was shown in FIG. 2) is the peripheral surface 2 andrake surface 6 (as was shown in FIG. 2), the surface on which the chipof removed material is formed, is one of the end surfaces 3 (upper endsurface 9). Alternatively, cutting insert 1 may be of tangential mounttype where rake surface 6 (as was shown in FIG. 3) is the peripheralsurface 2 and flank surface 5 (as was shown in FIG. 3) is upper endsurface 9. This invention promotes and enables the novel use of cuttinginserts that are unusually large in diameter relative to what isconventionally seen in round rotating inserts, typically less than 26 mmas in the Rotary Technologies Corp. Gen-II products and commerciallyavailable, down to 12 mm in the Pokolm Spinworx® product. In fact,making the insert larger in diameter is contrary to the commonplaceinclination to reduce the diameter of the round insert from the mindsetof saving on the valuable insert material and to reduce the amount ofprocess force directed into the surface being produced. However, byintroducing larger round rotating insert diameters from 25 mm up to,without limitation, 100 mm, the user achieves significantly more cuttingedge and machining time between insert changes and, in particular fortangential mount applications, may gain significant productivity bybeing able to run at much larger feed rates while maintaining a desiredsurface finish.

In this vein, the embodiment shown in FIG. 4a is generally for a cuttinginsert that is large in diameter relative to commercially availablestandard tapered roller bearings that generally, but without limitation,have a bore diameter greater than 15 mm, an outer diameter greater than35 mm, and axial dimension greater than 10 mm, or 25 mm fordouble-tapered roller bearings. In this embodiment, standarddouble-tapered roller bearings can generally be used more economicallythan a pair of single tapered roller bearings. In FIG. 4a , upperbearing 22 and lower bearing 23 oppose each other in their tapers,oriented relative to each other as shown in FIG. 4a or with their tapersboth opposite that shown in FIG. 4a . Their respective outer raceways,often referred to as “cups”, (upper outer raceway 24 with upper includedangle 24 a and lower outer raceway 25 with lower included angle 25 a(note that callout is broken in order to fit in figures; note also thatlower included angle 25 a is defined relative to the same reference asfor upper included angle 24 a, resulting in lower included angle 25 abeing greater than 180°, as shown)) are held compressed together axiallyin housing 26 between axial stop 27 and axial retainer 28, with spacer27 a as needed. In the case shown in FIG. 4a , generally but withoutlimitation, upper included angle 24 a is in the range of 10° to 120°inclusive and lower included angle 25 a is in the range of 240° to 350°inclusive. If the tapers are oriented opposite that shown in FIG. 4a ,then, generally but without limitation, upper included angle 24 a is inthe range of 240° to 350° inclusive and lower included angle 25 a is inthe range of 10° to 120° inclusive. Housing 26 along with upper outerraceway 24 and lower outer raceway 25 together serve as the stator.

An alternative is to integrate the bearing surfaces of upper outerraceway 24 and lower outer raceway 25 directly into housing 26 as shownin FIG. 4b . Either approach (FIG. 4a or FIG. 4b ) is acceptable withFIG. 4b being generally more compact and lower cost, especially if acommercially available standard double-taper bearing set meets thesizing requirements, in which case the combined outer raceways (combinedupper and lower cups) may at the same time also serve as housing 26. Inthis arrangement, generally but without limitation, upper included angle24 a and lower included angle 25 a would be in the ranges notedpreviously. Housing 26 with integral outer raceways (and respectivebearing surfaces) serves as the stator.

In either case (FIGS. 4a and 4b ), plain bearings (sliding surfaces) maybe used instead of rolling-element bearings. In any case, rotor 29passes through upper inner raceway 30 and lower inner raceway 31 (oftenreferred to as “cones”), which are compressed together axially by rotorupper end 37 and preload fastener 32 that engages with rotor lower end33. The included angles associated with the inner raceways are such thatthey match the included angles of their respective outer racewaysadjusted according to the taper angle of the rollers separating therespective inner and outer raceways. FIG. 4a illustrates preloadfastener 32 to be a nut that engages with a rotor lower end 33 that isthreaded. Shown also is preload element 34, which is optional, but whenincluded will allow more precise control when setting the preload.Preload fastener 32 could alternatively be a screw that engages into athreaded hole in rotor lower end 33, again optionally with or without apreload element 34. Preload element 34 is shown as a washer, but may beany other suitable element in material and/or shape so as to provide anacceptable level of compliance to allow adjustment of the preloadthrough tightening preload fastener 32, but also acceptable stiffnessfor function of the RSD in the machining process. Whether using a nut orscrew as preload fastener 32, in this case where preload fastener 32 isconcentric with rotor axis 36, some means of anti-rotation should beapplied, such as but not limited to a thread locking compound or a pinthat is non-coaxial with rotor axis 36, so preload fastener 32 will notinadvertently loosen under the rotary motion. FIG. 4b shows an alternateapproach where one or more preload fasteners 32 are used, threaded intoone or more preload holes 35 in rotor lower end 33, such that at leastone preload hole 35 is non-coaxial with rotor axis 36.

At rotor upper end 37 is the cutting insert interface which mates withrotor interface on cutting insert 1. In FIG. 4a the cutting insertinterface includes rotor pilot 38 that has at least a portion of itssurface cylindrical about and coaxial with rotor axis 36, and planarmounting surface 39. The rotor interface of cutting insert 1 includescylindrical surface 40, located in central hole 8, of which at least aportion is cylindrical about and coaxial with insert axis 4, and aplanar portion of lower end surface 11. Rotor pilot 38 and planarmounting surface 39 mate, respectively, with cylindrical surface 40 andplanar portion of lower end surface 11, such that insert axis 4 iscoaxial with rotor axis 36. Cutting insert 1, as noted in general, has aperipheral surface 2, and one end surface 3—the upper end surface 9—thatis opposite a second end surface 3—the lower end surface 11. Centralhole 8 passes through cutting insert 1 from upper end surface 9 to lowerend surface 11, said hole including cylindrical surface 40. Intermediateupper end surface 9 and central hole 8 is one or more fastener interfacesurfaces 10. In the embodiment shown in FIG. 4a one or more fastenerinterface surfaces 10 are counter-bored, though alternatively they maybe countersunk. For the large diameter cutting insert of thisembodiment, one or more threaded insert fastener elements 41, onecorresponding to each of the one or more fastener interface surfaces 10,axially clamp cutting insert 1 to rotor 29. The threaded insert fastenerelements 41 interface with one or more threaded insert fastenerreceivers 42 at least one of which is non-concentric with rotor axis 36.The fastener interface surface 10 may alternatively be comprised of asingle counter-bore or countersink about rotor axis 36. Cutting insert 1may be symmetric about its (horizontal) mid-plane. This allows cuttinginsert 1 to be flipped in order to make use of the other side forcutting after the first side is worn out.

FIG. 4b illustrates an alternative cutting insert interface thatincludes rotor convex surface 43, being convex relative to rotor upperend 37. Also shown is an alternate rotor interface on cutting insert 1that includes insert concave surface 44, which is concave relative toand located within and adjacent to lower end surface 11 of cuttinginsert 1. Central hole 8 of cutting insert 1 has one or more receivers45 running partially or fully through insert center thickness 46.Receivers 45 mate via loose slip fit to one or more protrusions 47 onrotor upper end 37. The mating of receivers 45 with protrusions 47 iscircumferential in nature, constraining cutting insert 1 from rotation,relative to rotor 29, about rotor axis 36, but not locating cuttinginsert 1 relative to rotor 29 in either the rotor axial or rotor radialdirections; said axial and radial locating of cutting insert 1 relativeto rotor 29 is accomplished with the mating of rotor convex surface 43with insert concave surface 44. The rotationally constraining(anti-rotation) nature of the receiver-protrusion mating allows a singlethreaded insert fastener element 41 to be used, one of its surfacesmating with a single fastener interface surface 10, on cutting insert 1,that is concentric with rotor axis 36, and its threaded portion engagingwith a single threaded insert fastener receiver 42 that is concentricwith rotor axis 36. Depending on the diametric size of central hole 8,it may be preferable or necessary to use a screw, as the threaded insertfastener 41, having a head that is smaller than central hole 8, in whichcase a fastener spacer 48 fills the space between the head of threadedinsert fastener element 41 and fastener interface surface 10, as shownin FIG. 4b . Furthermore, some embodiments could employ a threaded rotorupper end 37 with which a nut rather than a screw is used as thethreaded insert fastener element 41 that may mate directly with fastenerinterface surface 10 or by way of an intermediate fastener spacer 48depending on the relative sizes of the associated components. By makingupper end surface 9 and lower end surface 11 identical, that is, bymaking insert concave surface 44 identical to single fastener interfacesurface 10, both concentric with insert axis 4, cutting insert 1 may beflipped over so it can be used both ways, doubling the number of roundcutting edges useable for cutting, only one at a time however.

As shown in FIGS. 5a and 5b , when cutting insert 1 is of diameter largeenough to accommodate a bearing internal to central hole 8, an alternatebearing arrangement may be used to provide the desired axial and radialsupport and the preload as is inherent to this invention (to eliminateradial bearing clearance/gap/slop that is inherent to radial needlebearings like those in U.S. Pat. No. 4,477,211 and U.S. application Ser.No. 12/350,181). In the cases of FIGS. 5a and 5b , upper bearing 22 istapered as in the previous embodiments generally but without limitationexhibiting upper included angle 24 a in the range of 10° to 120°inclusive. Note that the rotating/stationary raceways are theouter/inner raceways in this embodiment, which is opposite theembodiments shown in FIGS. 4a and 4b where the rotating/stationaryraceways are the inner/outer raceways. Also different from theembodiments of FIGS. 4a and 4b , by being axially located generally orat least partially within central hole 8 of cutting insert 1, upperbearing 22 is capable of supporting the radial load on its own so thatlower bearing 23 need only provide axial load bearing capability. Thatis, lower bearing 23 may be an axial thrust roller bearing as shown inboth FIG. 5a and FIG. 5b ; common thrust roller bearings have includedangle 25 a of 180° (as defined here) and thus, in general, it may bemore appropriate to refer to lower bearing 23 as having a rotatingraceway, rather than an outer raceway, and a stationary raceway, ratherthan an inner raceway. As such, the terms stationary raceway androtating raceway may be used here to more generally indicate tworaceways of a bearing without specifically indicating which is inner andwhich is outer. Note that some thrust roller bearings employ taperedrollers in which case the included angle 25 a of the stationary racewaycould be greater than 180.

When cutting insert 1 has a large enough central hole 8 to accommodatethe cup of a commercially available standard tapered roller bearing,such a bearing can be used, meaning upper outer raceway 24 is separatefrom rotor 29 as shown in FIG. 5a . When cutting insert 1 has a centralhole 8 that is too small to accommodate the cup of a commerciallyavailable standard tapered roller bearing, its central hole may still belarge enough to accommodate upper bearing 22 internal to central hole 8if the upper outer raceway 24 (its bearing surface that is) is integralto rotor 29, as shown in FIG. 5b . Unlike the embodiments of FIGS. 4aand 4b , the stationary portion of the rotary support device, the“stator” (previously associated with housing 26) is partially internalto the bearings rather than exclusively external to the bearings. Assuch, preload element 34 is now at the top of the rotary support deviceand attaches to stator 49 rather than rotor 29 as was the case in theembodiments shown in FIGS. 4a and 4b . In FIGS. 5a and 5b , preloadelement 34 is attached to stator 49 by engaging preload fastener 32, asingle screw, with a threaded hole in stator upper end 50. Inadvertentloosening of preload screw 32 can be achieved with a thread locker asnoted earlier, or as shown here with a pin 34 a or a similaranti-rotation element.

In both FIGS. 5a and 5b , the similar insert mounting and support areused as in FIG. 4b with the exception that threaded insert fastenerelement 41 is a nut with its threaded portion engaging with a singlethreaded insert fastener receiver 42 that is a male thread concentricwith rotor axis 36, rather than a screw engaging a female threaded hole.In these embodiments there is no need for a fastener spacer 48 to fillthe space between the threaded insert fastener element 41 and fastenerinterface surface 10 on cutting insert 1. Again, inadvertent looseningof threaded insert fastener element 41 is avoided by one or morereceivers 45 on cutting insert 1 mating via loose slip fit to one ormore protrusions 47 on rotor upper end 37.

A final element of the embodiments shown in FIGS. 4a, 4b, 5a and 5b is aself-tightening, anti-incursion, compact rotary seal 51 (see FIGS. 6a,6b, and 6c for close-up views). It is termed “anti-incursion” since amain purpose is to keep contaminants from getting into the inside of theRSD and since pressure from the outside of the RSD causes the sealingcontact pressure to increase, not loosen. Rotary seal 51 comprises anelastic ring 52 that is stretched around primary seal surface 53 andinterfaces with secondary seal surface 54. All four figures (FIGS. 4a,4b, 5a and 5b ) indicate where this seal and respective surfaces arelocated in the respective embodiments. The cross-section shape ofelastic ring 52 may be round, square or lobed as seen in standard“O-rings”, but may be any shape, such as but not limited to rectangularor triangular. In the noted embodiments (FIGS. 4a, 4b, 5a and 5b )primary seal surface 53 is located at the housing upper end 47 on theouter diametric surface of housing 26 and secondary seal surface 54 islocated on rotor 29. In FIGS. 5a and 5b there is a second use of thisseal where primary seal surface 53 is on preload element 34 andsecondary seal surface 54 is on rotor upper end 37.

FIG. 6a shows the general nature of the self-tightening, anti-incursion,compact rotary seal 51 by itself. Primary seal surface 53 isaxisymmetric about axis of rotation 55, equivalently in theseapplications referred to as rotor axis 36. Primary seal surface 53 maybe conical, but more generally (as shown in FIG. 6a ) is described suchthat primary tangent plane 56, being a plane placed at a point on andtangent to primary seal surface 53, is oriented relative to axis ofrotation 55 with primary angle 57 (referred to as θ_(p)) greater thanarctan μ_(p), μ_(p) being the coefficient of friction between elasticring 52 and primary seal surface 53, and less than 89°.

The seal functions by stretching elastic ring 52 around primary sealsurface 53. Because elastic ring 52 is elastic, that is, it can stretchfrom its original relaxed diameter to a larger stretched diameter, andreturn/shrink to a relaxed diameter that is near to or equal to itsoriginal relaxed diameter, its elastic tendency to shrink its diameterwill cause it to slide on primary seal surface 53 toward secondary sealsurface 54 until it makes contact with, and hence seals against,secondary seal surface 54. Secondary seal surface 54 may be conical, butmore generally (as shown in FIG. 6a ) is described such that secondarytangent plane 58, being a plane placed at a point on and tangent tosecondary seal surface 54, is oriented relative to axis of rotation 55with secondary angle 59 (referred to as Os) greater than primary angle57 (θ_(p)) and less than θ_(p)+90°. Increasing θ_(p) and/or(θ_(s)−θ_(p)) increases the sealing force acting between elastic ring 52and secondary seal surface 54, where the sliding motion occurs (i.e.,elastic ring 52 slides rotationally on secondary seal surface 54 and isrotationally stationary relative to primary seal surface 53). Sinceelastic ring 52 is stretched, wear of and dimensional tolerances in thecross-section and diameter of elastic ring 52 are offset by theself-tightening action of the seal system. FIGS. 6b and 6c illustrateother orientations of secondary seal surface 54 relative to primary sealsurface 53, where, for the sake of simplicity, these surfaces are shownas conical such that the tangent plane is the same at all points on therespective surface.

Many applications require a cutting insert that is smaller in diameterthan can be accommodated with the relatively large size of readilyavailable tapered roller bearings in the above embodiments. In thesecases, an embodiment similar to those in FIGS. 4a and 4b can be usedwhere generally all of the same components are employed but withsimplified tapered roller bearings that are easily manufactured withreadily available cylindrical roller elements (versusfrusto-conical/tapered roller elements that are needed for typicaltapered roller bearings). FIG. 7a shows such an embodiment. There stillexists an upper outer raceway 24 and lower outer raceway 25; since anobjective of this embodiment is to be very compact, like the embodimentshown in FIG. 4b , the outer raceways (cups) and their associatedbearing surfaces would generally but not necessarily be integral withhousing 26. The main difference is that the bearing rollers 61 arecylindrical and held in cages 62 that generally would differ fromcommercially available tapered roller cages. Using cylindrical rollersresults in some degree of sliding/skidding along with rolling on thecylindrical surfaces of the rollers, whereas actual tapered rollerbearings exhibit (theoretically) pure rolling on the tapered surfaces ofthe rollers if manufactured correctly/precisely. In the case ofcylindrical rollers, though not necessarily, rotor 29 can provide theupper inner bearing surface, that is, serve as the upper inner raceway30 to save space. A lower inner raceway 31 is attached to rotor lowerend 33 in the same way(s) and with the same components as describedearlier. FIG. 7a also shows a case where preload fastener 32 is a nutthat is integrated with lower inner raceway 31 and no preload element 34is used. FIG. 7b further shows another way of producing protrusions 47(six of them) on rotor upper end 37 that mate via loose slip fit withreceivers 45 on cutting insert 1, the mating being circumferential innature with cutting insert 1 located and supported radially and axiallyby rotor upper end 37 by way of insert concave surface 44 mating withrotor convex surface 43 (see FIG. 7a ).

The final embodiment of the rotary support device allows an end-user toadjust each cutting insert 1 in the field, after fully manufacturing thecutting tool on which one or more rotary support devices are attached.An example of this embodiment is shown in FIG. 8 as an extension of theembodiment of FIG. 7a . The main difference from the previousembodiments (FIG. 7a ) is that housing 26 (stator) is extended axiallyin the direction opposite rotor upper end 37. Integrated into thehousing lower end 71 (stator lower end) is wedge interface surface 72that is at a wedge angle 73 (wedge interface surface 72 is not visiblein cross-section but is indicated with a heavy dashed line) relative tobeing normal to rotor axis 36. Wedge angle 73 is generally, withoutlimitation, in the range of 1 to 20 degrees. A larger wedge angle 73will provide a larger range of adjustment, but also generally reducesthe resolution of adjustment actuation. Below and mating with wedgeinterface surface 72 is adjustment wedge 74 having stator interfacesurface 75 at substantially the same (opposing) wedge angle 73 so thatit mates with wedge interface surface 72. As indicated in FIG. 8 thisembodiment is best achieved by attaching a separate upper wedgeextension 77 to create the equivalent housing lower end 71 of thisembodiment.

The aforementioned set of components, housing 26 (i.e., the stator,having rotor 29, bearings and all other components, less a cuttinginsert 1, assembled to and into it), upper wedge extension 77 andadjustment wedge 74, are then placed into adjustment cavity 78 in outerhousing 79. Outer housing 79 is cylindrical on its outer surface forbeing inserted/assembled into a cylindrical pocket on a cutter body.Adjustment cavity 78 is generally also cylindrical, matching thegenerally cylindrical outer surface of housing 26 at their interface,the axis of which (adjustment cavity axis 80) may be parallel to outerhousing axis 81, or at an angle relative to outer housing axis 81 asshown in FIG. 8. To maintain force on the mating surface of theadjustment mechanism, that is wedge interface surface 72 and statorinterface surface 75, a wedge preload screw 82 passes through preloadspring 83 then through, from outside of (below), spring cavity bottom84, then through adjustment wedge 74, and ultimately threaded intopreload screw hole 85 in support housing lower end 71 or upper wedgeextension 77 as employed in connection to housing lower end 71.

Translation of adjustment wedge 74, specifically its cavity interfacesurface 74 a, along adjustment cavity bottom 86 is caused by turningadjustment screw 87 that passes through adjustment hole 88 in the sideof outer housing 79. This adjustment requires that adjustment screw 87cannot move along its adjustment screw axis 89. This is achieved withscrew head retainer 90. Screw head retainer 90 also serves to seal withthe mating surface on the outside of outer housing 79 to keep particlesof debris, and most of the liquid that may spray on the tool, fromentering into adjustment cavity 78 that would otherwise contaminate thecomponents contained therein. Translation of adjustment wedge 74, uponturning adjustment screw 87, occurs by way of the threaded interfacebetween adjustment screw 87 and adjustment screw hole 91 in adjustmentwedge 74. Shown in FIG. 8 is a locking screw 92 that serves to take upany clearance between the outer surface of housing 26 and the innersurface of adjustment cavity 78. The top of the adjustable RSD is sealedwith the earlier described anti-incursion compact rotary seal whereelastic ring 52, primary seal surface 53, and secondary seal surface 54are shown in FIG. 8.

In all cases where the included angle of the mating convex and concavesurfaces must be large, say greater than 90 degrees, it can be helpfulto include a diametral piloting of threaded insert fastener element 41,or fastener spacer 48, in a loose slip fit to rotor 29 to assist ininitially centering/seating cutting insert 1 on rotor upper end 37.

Some embodiments may benefit from cutting insert 1 having insert convexsurface 44 a (rather than concave as in previous embodiments), which isconvex relative to and located adjacent to lower end surface 11 ofcutting insert 1, between peripheral surface 2 and lower end surface 11.In this case, cutting insert interface on rotor 29 includes rotorconcave surface 43 a that is concave relative to rotor upper end 37.This is illustrated in FIG. 9.

Note that the approach to mounting a round cutting insert to a rotor byemploying a single cutting insert interface with the rotor, where arotor convex/concave surface mates with an insert concave/convexsurface, may be applied, either with or without one or moreanti-rotation protrusions 47 and receivers 45, to rotors that aresupported relative to the stator by different bearing arrangements thanare the subject of this invention.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the invention. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the invention.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the invention.

What is claimed is:
 1. A rotary seal comprising: a. an axis; b. aprimary seal surface having a primary tangent plane making a primaryangle with the axis less than 89°; c. a secondary seal surface having asecondary tangent plane making a secondary angle with the axis greaterthan the primary angle and less than the primary angle plus 90°; and d.an elastic ring stretched around the primary seal surface, whereby,through contraction, the elastic ring is predisposed to sliding toward,mating with, and forming a seal against the secondary seal surface. 2.The rotary seal of claim 1, in which the primary angle is greater thanthe arctangent of the coefficient of friction between the elastic ringand the primary seal surface.
 3. The rotary seal of claim 1, in whichthe elastic ring has a circular cross-section.
 4. The rotary seal ofclaim 1, in which the elastic ring has a square cross-section.
 5. Therotary seal of claim 1, in which the elastic ring has a rectangularcross-section.
 6. The rotary seal of claim 1, in which the elastic ringhas a lobed cross-section.
 7. The rotary seal of claim 1, in which theelastic ring has a triangular cross-section.